Around 2007, the National Institute for Occupational Safety and Health (NIOSH) introduced a concept known as prevention through design (PtD), which addresses preventing and controlling occupational injuries, illnesses and fatalities by “designing out” or minimizing hazards and risks. While this effort initially targeted LEED projects and designs, the benefits of employing such principles seemed to be obvious in all forms of construction. More information about PtD can be found on the Centers for Disease Control NIOSH website (bit.ly/2R5XziI).
This article takes a look at how PtD principles have significant benefits in the planning and preplanning phases of construction that result in safer projects while under construction and safer installations once construction is complete and occupancy is taken. Within this article, some prevention through design or safety by design philosophies will be reviewed as it relates to specific requirements in the National Electrical Code (NEC) and how electrical safety in the workplace is enhanced as a result.
Same purpose, different day
The NEC is an installation code that provides for the practical safeguarding of people and property from the hazards arising from the use of electricity. Compliance with the NEC will result in an installation that is essentially free from electrical hazards. While Section 90.1(A) clearly indicates that the NEC is not a design specification or a manual for untrained people, electrical designs and engineering should be such that compliance with the NEC requirements is achieved. The relationship between PtD concepts and the NEC is simply that if installation rules result in reduced risk of injury to workers or occupants that safety is built in to the installation.
Locking out a disconnecting means
Let’s take a look at some NEC rules that are directly related to electrical safety as covered by NFPA 70E, Standard for Electrical Safety in the Workplace. Section 110.25 requires installing provisions for use of a lock on switches or circuit breakers, whether or not the lock is installed. This rule directly supports the lockout/tagout requirements in Article 120 of NFPA 70E. With the main purpose of NFPA 70E focused on removal (elimination) of the electrical hazard as the first choice, this installation requirement directly supports the workplace safety rules.
Arc energy reduction and the NEC
Other recently added NEC rules that directly support PtD concepts are the requirements in Sections 240.67 and 240.87 for using a method of arc energy reduction for installations at or above the 1,200-ampere (A) level. For fuses, four methods are provided and for circuit breakers, seven methods are provided. These methods of arc energy reduction rely on reduction of time that an arcing event is sustained. Reducing the duration of the arc time reduces the amount of energy.
An important feature of these requirements is that documentation of the location of the fuse or circuit breakers be made available for those authorized to install, inspect, design or operate the installation. These requirements serve not only to reduce the arc energy for the equipment and building safety, but also provide significant benefits to those that may have to perform justified energized work on such protected equipment.
Some forward thinking is being applied to the next edition of the NEC to include more requirements that directly affect safety for equipment and workers in various occupancies. New requirements are being introduced that specify barriers in all equipment suitable for use as service equipment. The barriers serve to prevent inadvertent contact with service busbars as they did previously for just service switchboards and panelboards. The change requires this feature to be included on all equipment that is suitable for use in the service position, enhancing safety. Another revision that will enhance safety for workers is the requirement for a single main (service) disconnect within a single enclosure. The two to six service disconnects will no longer be acceptable when all service disconnects are installed in the same enclosure, such as a switchboard or panelboard. The two to six disconnect rule will still be allowed for up to six disconnects in separate enclosures that are grouped in the same location, as in previous editions of the NEC .
Coordination between the electrical installation ( NEC ) and the Standard for Electrical Safety in the Workplace (NFPA 70E) improve both installation safety and enhance safety for electrical workers, simultaneously. For more detailed information about the revisions forthcoming in the 2020 NEC, visit nfpa.org/70.